We propose a new information-theoretic metric, the symmetric Kullback-Leibler divergence (sKL-divergence), to measure the difference between two water diffusivity profiles in high angular resolution diffusion imaging (HARDI). Water diffusivity profiles are modeled as probability density functions on the unit sphere, and the sKL-divergence is computed from a spherical harmonic series, which grea...

2014 A laser pulse method for diffusivity determination is analysed. The method which permits the measurement of the laser pulse energy distribution as well as its shape is developed. This method can be easily implanted into laser pulse diffusivity set-up and it allows to check periodically the pulse characteristics that is of primary importance for the accuracy of the diffusivity measurements....

A novel transient technique is developed to measure the thermal diffusivity of one-dimensional microscale wires. In this technique, a pulsed nanosecond laser is used to quickly heat the wire. After laser heating, the wire temperature decays slowly. Such temperature decay is sensed and used to determine the thermal diffusivity of the wire. A 25.4μm thin Pt wire is characterized to verify this te...

It is well established that human brain white matter structure changes with aging, but the timescale and spatial distribution of this change remain uncertain. Cross-sectional diffusion tensor imaging (DTI) studies indicate that, after a period of relative stability during adulthood, there is an accelerated decline in anisotropy and increase in diffusivity values during senescence; and, spatiall...

The generation of solar non-axisymmetric magnetic fields is studied based on a linear α −Ω dynamo model in a rotating spherical frame. The model consists of a solarlike differential rotation, a magnetic diffusivity varied with depth, and three types of α-effects with different locations, i.e. the tachocline, the whole convective zone and the sub-surface. Some comparisons of the critical α-value...

This paper is intended to provide a stochastic approach involving the combined use of the Feynman-Kac formula and Monte Carlo method as a solution algorithm for estimating the timedependent effective diffusivity in a one-dimensional parabolic inverse problem. The inverse problem is purposed to design a mathematical model for the gas-diffusion process within the alveolar region of the human's lu...

The diffusivity of water, fucose, proline, lysine, glutamic acid, glucose and sucrose was determined in a variety of inflammatory human synovial fluids. In view of the constituents of pathological synovial fluids one would predict impedence to solute movement. In several fluid diffusivity was enhanced relative to translational diffusion in water. In most fluids diffusivity was enhanced relative...

The shear augmented dispersion of solutes in blood flow i through circular tube and ii between parallel flat plates is analyzed mathematically, treating blood as Herschel-Bulkley fluid model. The resulting system of nonlinear differential equations are solved with the appropriate boundary conditions, and the expressions for normalized velocity, concentration of the fluid in the core region and ...

BACKGROUND AND PURPOSE Cushing syndrome appears after chronic exposure to elevated glucocorticoid levels. Cortisol excess may alter white matter microstructure. Our purpose was to study WM changes in patients with Cushing syndrome compared with controls by using DTI and the influence of hypercortisolism. MATERIALS AND METHODS Thirty-five patients with Cushing syndrome and 35 healthy controls,...

We introduce a general purpose penetrator, fitted with a heater, for measuring temperature and thermal diffusivity. Due to its simplicity of deployment and operation the penetrator is well suited for remote deployment by spacecraft into a planetary regolith. Thermal measurements in planetary regoliths are required to determine the surface energy balance and to measure their thermal properties. ...